Microfluidics refers to devices and methods for controlling and manipulating fluid flows at length scales less than a millimeter. Miniaturization of a laboratory to a small device, usually termed as lab-on-a-chip, is an advanced technology that integrates a microfluidic system including channels, mixers, reservoirs, pumps and valves on a micro scale chip and can manipulate very small sample volumes of fluids. While several flow control concepts for microfluidic devices have been developed to date, here flow control concepts based on thermally responsive polymer solutions are presented. In particular, flow control concepts base on the thermally triggered reversible phase change of aqueous solutions of the polymer Pluronic will be discussed. Selective heating of small regions of microfluidic channels, which leads to localized gel formation in these channels and reversible channel blockage, will be used to control a membrane valve that controls flow in a separate channel. This new technology will allow generating inexpensive portable bioanalysis tools where microvalve actuation occurs simply through heaters at a constant pressure source without a need for large external pressure control systems as is currently the case. Furthermore, a concept for controlled cross-channel transport of particles and potentially cells is presented that relies on the continuous regeneration of a gel wall at the diffusive interface of two co-streaming fluids in a microfluidic channel.

A computer-controlled microfluidic extensional flow device is developed for trapping and manipulating micron-sized hard and soft particles. The extensional flow is generated in a diamond-shaped cross-slot that has each corner connected to a pressure-controlled liquid reservoir. By employing an imaging-based control algorithm, a particle can be made to move to an arbitrary position within the slot by adjusting the reservoir pressures and hence the fluid flow rates into/out of the slot. Thus, a soft particle can be trapped indefinitely at a point within the slot, and a known hydrodynamic force can be applied to study the dynamics of stretching and breakup of the particle. Alternatively, adhesion or coalescence dynamics of soft particles may be investigated by effecting a controlled collision between two particles. The device is validated by measuring the low interfacial tension of a compatibilized oil-water interface.

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No description available.

A computer-controlled microfluidic extensional flow device is developed for trapping and manipulating micron-sized hard and soft particles. The extensional flow is generated in a diamond-shaped cross-slot that has each corner connected to a pressure-controlled liquid reservoir. By employing an imaging-based control algorithm, a particle can be made to move to an arbitrary position within the slot by adjusting the reservoir pressures and hence the fluid flow rates into/out of the slot. Thus, a soft particle can be trapped indefinitely at a point within the slot, and a known hydrodynamic force can be applied to study the dynamics of stretching and breakup of the particle. Alternatively, adhesion or coalescence dynamics of soft particles may be investigated by effecting a controlled collision between two particles. The device is validated by measuring the low interfacial tension of a compatibilized oil-water interface.

Thesis (Ph. D.)--Auburn University, 2009. / Abstract. Vita. Includes bibliographical references (p. 168-174).

Thesis--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 78-81).

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 61-63). Also available on the World Wide Web.

Thesis (M.Sc.Eng.)PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / The exploration and production of oil and gas resources require innovative information acquisition strategies for wellbore environments to improve reservoir management. In this study, a microfluidic channel data retrieval platform was proposed for multiple sensor chip manipulation, wireless charging and information extraction in fluidic mediums. The working principle of near-field magneto inductive coupling was investigated and a prototype of a microfluidic channel integrated with a spiral reader antenna was designed and fabricated. Sensor chip manipulations and dynamic couplings between readers and sensors were demonstrated inside the proposed microfluidic channel. Furthermore, solid fluidic interaction between sensors and flows was analyzed. Comsol simulation was conducted to quantitatively characterize flow drag forces inside the channel. To prevent communication interference between sensors in the proposed coupling region, sensor separation strategies based on side channel and meander channel design were proposed and realized to separate sensors one by one by the desired distance. To enhance the efficiency of the sensor separation process, a new channel design based on a spinning blade with real-time image processing was also developed for feedback control of separation. Additionally, a 500-micron cubic sensor antenna was cut by a dicing saw and assembled into an 800-micron cubic package. Magneto inductive couplings between readers and the assembly package were conducted out of the channel. The results show that the coupling effect is strongly related with the orientation between the reader and the assembly package. Finally, the assembly package control with desired velocity and direction in oil mediums was successfully realized inside the channel. / 2031-01-01

Thesis (M.Sc.Eng.) PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Silk fibers from arthropods possess several favorable properties for biomedical applications, including high mechanical strength and biocompatibility. However, the majority of silk fiber production is currently limited to manipulation of cocoons from the Bombyxmori silkworm. The efficiency of the process can be increased by dissolving waste silk threads and using artificial spinning techniques to spin the proteins back into usable fibers. Once an artificial spinning technique has been perfected, it may be possible to use similar designs to spin recombinant silk proteins into threads with more favorable mechanical properties. The first step towards customizable silk is to artificially spin silk protein into fibers with comparable properties to naturally-derived silk threads. Current microfluidic devices are limited to spinning B. mori silk into weak, poorly-formed fibers. The incorporation of silk gland-like ion gradients and high shear stress into current and novel microfluidic devices is theorized to improve mechanical properties of resultant spun silk. To this end, ion gradients were added to the current microfluidic device. In addition, a novel microfluidic device was developed to increase shear stress. After investigating the individual effects of ion gradients and shear stress on the silk spinning process, an integrated microfluidic device was designed to investigate the combined effects. Computational models of the flow within each microfluidic device were generated and used to predict biomimetic design parameters. Measurements of fiber diameter and pH within the microfluidic devices were collected to verify the accuracy of the computational models. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and mechanical testing measurements were collected to characterize and compare resultant fibers. From these results, relationships were found between the incorporation of ion gradients and shear stress into the spinning process and the properties of the fibers produced. / 2031-01-01